1. Field of the Invention
The present invention relates to a farm machine comprising at least one group of working elements and a structure equipped in particular with a hitching mechanism making it possible, during the use of the farm machine, to hitch the latter to a motor vehicle. The group of working elements is connected to the structure by a deformable quadrilateral suspension device comprising suspension elements connected, on the one hand, to the structure by first joints and, on the other hand, to the group of working elements by second joints.
2. Description of the Related Art
A pulled mower comprising a frame which extends crosswise to the direction of advance at work is known. At each of its ends, this frame is equipped with a wheel by which it rests on the ground. In the median part, the frame is connected to a tongue which makes it possible to hitch the mower to a tractor and which is connected to the frame by a joint with vertical axis. The frame supports a group of working elements by a deformable parallelogram suspension device. This device comprises two pairs of connecting rods each extending near one end of the frame.
A mower intended to be hitched to the front hitch of a tractor and whose group of mowing elements is also connected to the frame by a deformable parallelogram suspension device is also known. The frame of this known mower comprises a central bracket which is equipped at its rear part with a hitching triangle making it possible to hitch the mower to the front hitch of the tractor and which extends above the group of mowing elements. The latter is connected to the front part of the bracket by the deformable parallelogram device which comprises three connecting rods: one upper connecting rod and two lower connecting rods. The upper connecting rod is connected to the bracket by a first ball joint and to the mowing group by a second ball joint. The two lower connecting rods are each connected to the bracket by a ball joint and to the mowing group by a cylindrical joint. Moreover, they extend in top view at least approximately parallel in the direction of advance at work, so that the ball joints of the two lower connecting rods are very distant from one another.
Because of the deformable parallelogram, the group of working elements of these known machines can go up and down freely. The pivoting of the group of working elements around a straight line directed forward can be achieved in the first machine, only because the two pairs of connecting rods are relatively distant from one another and, in the second machine, only because the cylindrical joints comprise relatively significant plays. In all cases, however, this pivoting is relatively limited.